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JEE Main 202120 JulyMorning Shift
Exam
JEE Main
Year
2021
Date
20 July
Shift
Morning Shift
Subject
Chemistry
Chapter
Surface Chemistry

JEE Main 2021 · 20 July · Morning Shift · Chemistry · Surface Chemistry

The conditions given below are in the context of observing Tyndall...

The conditions given below are in the context of observing Tyndall effect in colloidal solutions:
(A) The diameter of the colloidal particles is comparable to the wavelength of light used.
(B) The diameter of the colloidal particles is much smaller than the wavelength of light used.
(C) The diameter of the colloidal particles is much larger than the wavelength of light used.
(D) The refractive indices of the dispersed phase and the dispersion medium are comparable.
(E) The dispersed phase has a very different refractive index from the dispersion medium. Choose the most appropriate conditions from the options given below:

Options

  1. A(A)( A ) and (E)( E ) only
  2. B(C)( C ) and (D)( D ) only
  3. C(A)( A ) and (D)( D ) only
  4. D(B)( B ) and (E)( E ) only

Correct answer

A. (A)( A ) and (E)( E ) only

Step-by-step solution

The phenomenon of scattering of light by colloidal particles as a result of which the path of the beam becomes visible is called a tyndall effect. Smaller the diameter and similar the magnitude of refractive indices, lesser is the scattering and hence the tyndall effect and viced-versa. The diameter of the dispersed phase particle should not be smaller than the wavelength of light used because they won't be able to scatter the light so, therefore, the diameter of the dispersed particles should be equal or not much smaller than the wavelength of the light used.
2. The refractive indices (i.e. the ratio of the velocity of light in vacuum to the velocity of light in any medium) of the dispersed phase and the dispersion medium should differ greatly in magnitude than only the particles will be able to scatter the light and tyndall effect will be observed. On the other hand, if the refractive indices of the dispersed phase and dispersion medium are almost similar in magnitude, then there will be no scattering of light and hence, therefore, no tyndall effect is observed.
Hence answer AA and EE are correct.

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